This application relates to a cooling system for cooling air in a gas turbine engine by heating fuel, and wherein an intermediate fluid is utilized to perform the heat exchange.
Gas turbine engines are known, and typically include a compressor for compressing air and delivering it downstream into a combustion section. The compressed air is mixed with fuel and combusted in the combustion section. The products of this combustion are then delivered downstream over turbine rotors which are driven to rotate, to provide power to the engine.
The turbine rotors are subjected to very high temperatures by the products of combustion. Thus, it is known to tap cooling air and deliver that cooling air to components of the turbine section to cool those components.
However, competing with this use of air is the goal to provide higher pressure ratios at the compressor for improved combustion. As the pressure ratios increase, so does the air temperature. Thus, the air downstream of the compressor is less useful as cooling air since it becomes hotter to provide the higher pressure ratios.
It has been proposed to cool the air downstream of the compressor by exchanging heat in the air to fuel being delivered into the combustion section. Generally, this has been performed by placing the air and fuel in close heat exchange relationship.
This is somewhat undesirable, in that having quantities of cooling air in the vicinity of the fuel makes any air or fuel leakage more risky.